Distraction osteogenesis fixture

ABSTRACT

A distraction osteogenesis fixture to be anchored in a bone, including a lower anchor, a translational screw, and an upper anchor. At least a portion of the lower anchor is externally threaded. At least a portion of the lower anchor includes an anti-rotational feature. The lower anchor includes an internal passage. At least a portion of the internal passage is threaded. At least a portion of the translational screw is externally threaded such that the translational screw is receivable by the threaded internal passage of the lower anchor. The upper anchor includes an internal passage for receiving a portion of the lower anchor and has an anti-rotational feature for engaging the anti-rotational feature of the lower anchor. The internal passage of the upper anchor includes a surface for engaging the translational screw. At least a portion of the upper anchor is externally threaded.

FIELD OF THE INVENTION

The invention relates to a method and device for increasing bone size ormass. In particular, the present invention relates to a method andapparatus for distraction osteogenesis. The present invention especiallyrelates to increasing size of a portion of a patient's jawbone.

BACKGROUND OF THE INVENTION

In the context of certain medical and dental procedures, it may bedesirable to increase the volume of bone at certain locations. Thedesire to increase bone volume may arise from a desire to strengthen aweak area in a bone. Another reason for increasing bone volume is toprovide sufficient volume to accommodate a device implanted into thebone.

One method for increasing bone volume involves removing bone from onepart of the body and transplanting to the area where it is desired toincrease the bone volume. Bone implant procedures involve major surgeryand disruption to the patient's body, wherein a patient's body isopened. Bone to be transplanted is then physically removed from a bonewith saws and/or chisels, for example. One area where bone is oftenremoved from is the ribs, another is the hip. The area that the bone isto be transplanted to is then cut open and a proper site prepared forreceiving the transplanted bone. The transplanted bone is thentransferred to the site. Bone transplant typically involves majorsurgery involving full anesthesia.

An alternative to bone implant surgery for increasing bone volumeinvolves a process known as distraction osteogenesis. In distractioncsteogenesis procedures, bone is stretched. Typically, an incision ismade between two portions of bone and the portions of bone are thenslowly separated from each other. It is desired that the space createdby a separation of the bone portions is then filled in by new bone.

SUMMARY OF THE INVENTION

The present invention provides a distraction osteogenesis fixture. Thefixture includes a lower anchor to be anchored in a jawbone. At least aportion of the lower anchor is externally threaded. Additionally, atleast a portion of the lower anchor includes an anti-rotational feature.The lower anchor also includes an internal passage. At least a portionof the internal passage is threaded. The fixture also includes atranslational screw. At least a portion of the translational screw isexternally threaded such that the translational screw is receivable viathreaded internal passage of the lower anchor. The fixture furtherincludes an upper anchor having an internal passage for receiving aportion of the lower anchor and has an anti-rotational feature forengaging the anti-rotational feature of the lower anchor. The internalpassage of the upper anchor includes a surface for engaging thetranslational screw. At least a portion of the upper anchor isexternally threaded.

The present invention also provides a distraction osteogenesis method.The method includes forming a hole in a bone of a patient. Thedistraction osteogenesis fixture, including a lower anchor, an upperanchor, and a translational screw, is inserted into the hole. The loweranchor includes an externally threaded portion, an anti-rotationalfeature, and a threaded internal passage. The translational screw of thedistraction osteogenesis fixture is inserted into the threaded internalpassage of the lower anchor. An upper anchor of the distractionosteogenesis fixture is attached over the anti-rotational feature of thelower anchor and over the translational screw. The upper anchor includesan internal passage for receiving a portion of the lower anchor and hasan anti-rotational feature for engaging the anti-rotational feature ofthe lower anchor. The internal passage of the upper anchor includes asurface for engaging the translational screw. At least a portion of theupper anchor is externally threaded. At least the cortical portion ofthe bone is cut. The translational screw is then rotated so as to causelinear translational movement of the upper anchor relative to the loweranchor, whereby the bone surrounding the upper anchor is moved away fromthe bone surrounding the lower anchor.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription, wherein there are shown and described only the preferredembodiments of the invention, simply by way of illustration of the bestmode contemplated of carrying out the invention. As will be realized,the invention is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects, without departing from the invention. Accordingly, thedrawings and description are to be regarded as illustrative in natureand not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned objects and advantages of the present invention willbe more clearly understood when considered in conjunction with theaccompanying drawings, in which:

FIG. 1 represents a side plan view of an embodiment of a lower anchor ofan embodiment of a distraction osteogenesis fixture according to thepresent invention;

FIG. 2 represents a cross-sectional view of the embodiment of the loweranchor illustrated in FIG. 1 taken along the plane 2—2 illustrated inFIG. 1;

FIG. 3 represents a bottom plan view of the embodiment of the loweranchor illustrated in FIG. 1 and FIG. 2;

FIG. 4 represents a top plan view of the embodiment of the lower anchorillustrated in FIG. 1 and FIG. 2;

FIG. 5 represents a close-up cross-sectional view of a portion of anexternally threaded portion of the lower anchor illustrated in FIG. 1and FIG. 2;

FIG. 6 represents a side plan view of an embodiment of a translationalscrew according to an embodiment of a distraction osteogenesis fixtureaccording to the present invention;

FIG. 7 represents a cross-sectional view of the embodiment of thetranslational screw illustrated in FIG. 6 taken along the plane 7—7illustrated in FIG. 6;

FIG. 8 represents a bottom plan view of the embodiment of thetranslational screw of the present invention illustrated in FIG. 6 andFIG. 7;

FIG. 9 represents a top plan of the translational screw illustrated inFIG. 6 and FIG. 7;

FIG. 10 represents a side plan of an embodiment of an upper anchor of anembodiment of a distraction osteogenesis fixture according to thepresent invention;

FIG. 11 represents a cross-sectional view of the embodiment of the upperanchor illustrated in FIG. 10 taken along the plane 11—11 illustrated inFIG. 10;

FIG. 12 represents a close-up cross-sectional view of an end of theembodiment of the upper anchor illustrated in FIG. 10 taken along theline 12—12 in FIG. 13;

FIG. 13 represents a bottom end plan view of the embodiment of the upperanchor illustrated in FIG. 10;

FIG. 14 represents a top plan view of the embodiment of the upper anchorillustrated in FIG. 10;

FIG. 15 represents a close-up cross-sectional view of a portion of athreaded exterior portion of the embodiment of the upper anchorillustrated in FIG. 10;

FIG. 16 represents a cross-sectional view of an embodiment of a depthgauge that may be utilized with a distraction osteogenesis fixtureaccording to the present invention;

FIG. 17 represents a top view of the embodiment of the depth gaugeillustrated in FIG. 16;

FIG. 18 represents a side view of an embodiment of a retaining screw ofan embodiment of a distraction osteogenesis fixture according to thepresent invention;

FIG. 19 represents a top plan view of the embodiment of the retainingscrew illustrated in FIG. 18;

FIG. 20 represents a side view of an embodiment of a cap screw portionof an embodiment of a two piece healing cap of an embodiment of adistraction osteogenesis fixture according to the present invention;

FIG. 21 represents a top plan view of the embodiment of the cap screwillustrated in FIG. 20;

FIG. 22 represents a cross-sectional view of an embodiment of a cylinderof an embodiment of a two piece healing cap of an embodiment of adistraction osteogenesis fixture according to the present invention;

FIG. 23 represents a bottom plan view of the embodiment of the healingcap cylinder illustrated in FIG. 22;

FIG. 24 represents a top plan of the embodiment of the healing capcylinder illustrated in FIG. 22;

FIG. 25 illustrates a cross-sectional view of an embodiment of a manualfixture counter torque of an embodiment of a distraction osteogenesisfixture according to the present invention;

FIG. 26 illustrates a top plan view of the embodiment of the manualfixture counter torque illustrated in FIG. 25;

FIG. 27 illustrates a side plan view of the embodiment of the manualfixture counter torque illustrated in FIG. 25 and FIG. 26;

FIG. 28 represents a side plan of an embodiment of a fixture mount capscrew according to an embodiment of a distraction osteogenesis fixtureaccording to the present invention;

FIG. 29 represents a side plan view of a cylinder of an embodiment of afixture mount according to an embodiment of a distraction osteogenesisfixture according to the present invention;

FIG. 30 represents a side plan view of an embodiment of a lower anchorand a translational screw according to a distraction osteogenesisfixture according to the present invention, when partially assembled;

FIG. 31 represents a side plan view of an embodiment of a fullyassembled distraction osteogenesis fixture according to the presentinvention;

FIG. 32 represents a side plan view of the assembled distractionosteogenesis fixture according to the present invention also including aretaining screw;

FIG. 33 represents a side plan view of the embodiment of the distractionosteogenesis fixture illustrated in FIG. 30, FIG. 31 and FIG. 32 alsoincluding a healing cap;

FIG. 34 represents a side plan view of an embodiment of a distractionosteogenesis fixture with an attached fixture mount;

FIG. 35 represents an x-ray illustrating an embodiment of a distractionosteogenesis fixture implanted in a patient's jawbone wherein a piece ofthe jawbone has been separated from the patient's jawbone by about 0.5mm;

FIG. 36 represents an x-ray illustrating the fixture shown in FIG. 35wherein the piece of the jawbone has been separated from the jawbone byabout 4.5 mm; and

FIG. 37 illustrates a depth gauge attached to the upper anchor.

DETAILED DESCRIPTION OF THE INVENTION

Distraction osteogenesis is a process whereby bone is stretched toincrease bone volume. According to distraction osteogenesis processes,at least one portion of a bone is at least partially separated from thebone. The position of the portion is gradually altered with respect tothe bone. Time is then provided for new bone to fill in the spacebetween the portion and the overall bone.

Distraction osteogenesis is particularly useful in dental applications.In dental applications, a portion of a patient's jawbone will be atleast partially severed from the overall jawbone. The jawbone segmentmay then be gradually separated from the rest of the jawbone. New bonethen fills in the space between the segment and the jawbone. Byincreasing the volume of bone in the jawbone, additional area can beprovided to anchor or at least more securely anchor dental implants.Distraction osteogenesis can also be used in dental applications simplyto strengthen a location on the jawbone to increase the bone volume atthat location even if implants are not to be secured in the jawbone atthat location.

Typical devices utilized in distraction osteogenesis, especially indental applications, include a device or fixture that is secured toexterior of the jawbone. On the other hand, the present inventionprovides a device for distraction osteogenesis that may be implantedinto the bone. An advantage of the present invention is that at least aportion of the distraction osteogenesis fixture may be utilized in adental implant application after carrying out the distractionosteogenesis process. Alternatively, the present invention may also becarried out utilizing a resorbable material such that the fixture of theinvention is absorbed into the bone after the distraction osteogenesisprocess.

According to one embodiment, a distraction osteogenesis fixtureaccording to the present invention includes a lower anchor, atranslation screw, and an upper anchor. FIG. 1 illustrates an embodimentof a lower anchor according to the present invention. At least a portionof the exterior surface of the lower anchor is threaded. The embodimentof the lower anchor 1 illustrated in FIG. 1 includes externally threadedportion 3.

The portion of the length of the lower and upper anchors that areexternally threaded may vary depending upon the embodiment. It is theassembled lower and upper anchors, i.e. the osteogenesis fixture, thatis screwed into a hole formed in the bone. Accordingly, typically, thelength of the threaded portions of the lower and upper anchors accordingto the present invention is sufficient to help ensure that the fixturewill be secured in the bone. Additionally, the characteristics, such asthe dimensions and angles of the threads, may be varied from embodimentto embodiment to help ensure retention of the lower anchor in the bone.Typically, the externally threaded portion of the lower anchor includesright-hand threads.

To help facilitate insertion of the distraction osteogenesis fixtureinto a hole in a bone, the end of the lower anchor 1 to be inserted intothe hole may include at least one scalloped flute 5. The embodimentillustrated in FIG. 1 includes four symmetrically scalloped flutes 5.The scalloped flutes may help to facilitate securing of the lower anchorinto the hole in the bone by providing a volume for material in the holeor scraped from the side of the hole to be accommodated. The edges 7 ofthe scalloped flutes may also help to scrape away portions of the bonewithin the hole to facilitate insertion of the lower anchor.

The lower anchor may also include an anti-rotational feature. Theanti-rotational feature may be accommodated on at least a portion of thelower anchor. The anti-rotational feature helps to prevent rotation ofthe lower anchor and other element(s) placed thereon relative to eachother. For example, the anti-rotational feature may help to preventrelative rotation of the lower anchor and an upper anchor placedthereon, as described in greater detail below.

In the embodiment illustrated in FIG. 1, the anti-rotational featureincludes a shaft 9 having a hexagonal cross-sectional shape. If theanti-rotational feature includes a shaft having a particularcross-sectional shape, the length of the shaft that includes theparticular cross-sectional shape may vary depending upon a number offactors. For example, the distance or separation to be created by thedistraction osteogenesis may determine the length of the shaft includingthe anti-rotational feature. Preferably, the length and cross-sectionalarea of a shaft that includes an anti-rotational feature is sufficientto prevent deformation of the shaft during movements of the distractionosteogenesis fixture according to the present invention.

If the anti-rotational feature includes a shaft having a particularcross-sectional shape on the lower anchor, the cross-sectional shape mayvary. For example, rather than being a hexagon, the cross-sectionalshape could be square or octagonal or any other desired shape.Additionally, it is not necessary that the anti-rotational featureinclude a shaft on the lower anchor engaged by a correspondingly shapedpassage in the upper anchor. Other anti-rotational features may beutilized. One of ordinary skill in the art would be able to determine anappropriate anti-rotational feature once aware of the disclosurecontained herein.

The lower anchor of the distraction osteogenesis fixture according tothe present invention may also include an internal passage. At least aportion of the internal passage may be threaded. As seen in theembodiment illustrated in FIG. 1, the externally threaded portion of thelower anchor may have a greater diameter or cross-sectional area than ashaft including an anti-rotational feature.

The relative portions of the lower anchor that are externally threadedand that include an anti-rotational feature may vary depending upon theembodiment. According to one embodiment, more than one-half of thelength of the lower anchor includes an anti-rotational feature. Theexternally threaded portion of the lower anchor may represent less thanone-half of the length of the lower anchor. By including ananti-rotational feature that includes a shaft such as shaft 9illustrated in FIG. 1 wherein the shaft has a smaller diameter than theexternally threaded portion, the intersection 11 between the shaft andthe externally threaded portion may act as a stop for limiting andproviding a stop for the upper anchor when it is assembled on the loweranchor.

Internal passage 13 in the embodiment of the lower anchor illustrated inFIGS. 1-4 may accommodate a translational screw as described below ingreater detail. In the distraction osteogenesis fixture according to thepresent invention, the threads of the internal passage 13, or anythreaded portions of any portion of the distraction osteogenesisfixture, may be left handed or right handed. Although it may bedesirable for certain threaded portions to have a handedness oppositefrom other threaded portions. The depth of the internal passage 13 ofthe lower anchor may vary depending upon the amount of separationbetween the bone segment and the bone that it is desired to create.

According to one example of a lower anchor according to the presentinvention, the length of the anchor from end to end is about 13.25 mm, ±about 0.2 mm. The length of the shaft 9 including the anti-rotationalfeature may be about 7 mm. The width of the externally threaded portion,measured from the roots of the threads may be about 4.25 mm. The tip 15of the lower anchor 1 to be inserted into the hole in the bone may beabout 3.7 mm at its base. Each scalloped flute may have a length ofabout 3 mm. Additionally, the width of the anti-rotational shaft, takenbetween parallel sides of the hexagon may be about 2.72 mm. According toone embodiment, the depth of the internal passage of the lower anchor isabout 11.5 mm. This passage may include a threaded portion of about 10mm. The external threads on the lower anchor may have crests spacedabout 0.6 mm apart while the angle of the threads may be about 60°. Ofcourse, the above dimensions only represent example of a lower anchoraccording to the present invention. The dimensions may change based uponthe application.

The present invention also includes a translational screw. FIG. 6illustrates an embodiment of a translational screw 17. At least aportion of the external surface of the translational screw is threadedso that at least the externally threaded portion of the translationalscrew is receivable via the threaded internal passage of the loweranchor. Accordingly, the external threads of the translational screw maybe complimentary to the internal threads of the internal passage of thelower anchor. Along these lines, if the internal threads of the loweranchor are left handed, then the external threads of the translationalscrew should be left handed. The embodiment of the translational screw17 illustrated in FIG. 6 includes an externally threaded portion 19.

The translational screw may include a surface for engaging a surface ofan upper anchor as described below in greater detail. The exact form ofthe inter engaging surfaces of the translational screw in the upperanchor may vary, depending upon the embodiment. The embodiment of thetranslational screw illustrated in FIG. 6 includes a first or upper andregions of differing diameters in the vicinity of an end 21 of thetranslational screw opposite the end that the external threads areprovided in the vicinity of.

The embodiment of the translational screw according to the presentinvention illustrated in FIG. 6 includes a region of a first diameter 23closest to the end 21. This embodiment of the translational screw alsoincludes a region having a second diameter 25 having a greater diameterthan region 23. Region 25 is arranged on the translational screw at agreater distance from the end 21 than region 23.

Regions 23 and 25 of different diameters may be joined by a step 27. Itis the surface of step 27 that may engage a surface of upper anchor toapply force to the upper anchor to result in lateral translationalmovement of upper anchor relative to the lower anchor The regions 23 and25 may have cylindrical cross-sections. As a result, step 27 may have anannular shape. Step 27 and region 25 may be interconnected with region23 by a frustoconical region 29. Region 29 may facilitate manufacture ofthe screw by helping, for example, to make the a cleaner cut andeliminate metal chips that otherwise could disturb the surface of step27.

The translational screw may also include a region of reduced diameter 35extending between the externally threaded portion 19 and the upperanchor engaging portions 23 and 25.

The translational screw may also include an internal passage 31, as inthe embodiment illustrated in FIG. 6. At least a portion of the internalpassage 31 may be threaded. The threaded internal passage of thetranslational screw may receive, among other things, a retaining screw,and a healing cap. The threads of the internal passage of thetranslational screw may be right handed or left handed. Typically, thehandedness of the threads of the internal passage of the translationalscrew of the present invention is opposite as compared to the externalthreads of the translational screw.

The length and dimensions of the threads of the external threads of thetranslational screw may depend upon the desired degree of lateraltranslational movement of the translational screw with respect to thelower anchor that it is desired the distraction osteogenesis fixturepermit.

According to one embodiment of a translational screw according to thepresent invention, the overall length of the translational screw isabout 10.5 mm. The threaded portion of the exterior of the translationalscrew is about 5.5mm ± about 0.5 mm. The tip 33 of the translationalscrew may be beveled. The beveling may be about 45° with respect to themajor axis of the translational screw. Typically, the bevel on the tip33 of the translational screw matches a correspondingly angled bevel atthe base of the internal passage of the lower anchor. The region ofreduced diameter 23 may have a length at least of about 1.65 mm. If thefrustoconical region 29 is included, the length of the upper anchorengaging portion having a reduced diameter has a length of about 1.85mm. On the other hand, the length of the region 25 having a largerdiameter than region 23 may be about 0.65 mm. The difference indiameters of these two regions may be about 0.2 mm.

A distraction osteogenesis fixture according to the present inventionalso includes an upper anchor. FIG. 10 illustrates an embodiment 37 ofan upper anchor according to the present invention. The upper anchorengages the lower anchor and the translational screw as describedherein.

The upper anchor illustrated in FIG. 11 includes an internal passage 39for receiving a portion of the lower anchor. The internal passage 39 ofthe upper anchor includes an anti-rotational feature for engaging theanti-rotational feature of the lower anchor. Therefore, the structure ofthe anti-rotational feature of the upper anchor is interdependent uponthe structure of the anti-rotational feature of the lower anchor.

The internal passage 39 of the upper anchor 37 illustrated in FIGS. 10and 11 includes a portion that has a hexagonal cross-sectional shapecomplementary to the hexagonal cross-sectional shape of theanti-rotational feature of the lower anchor illustrated in FIG. 1.However, as described above, the anti-rotational feature may have anyconfiguration that permits it to engage the anti-rotational feature ofthe lower anchor and thereby prevent rotation of the upper anchorrelative to the lower anchor when the upper anchor and the lower anchorare engaged with each other. Typically, the cross-sectional area of thehexagonal shaped anti-rotational feature of the upper anchor is onlyslightly larger than the cross-sectional area of the hexagonalanti-rotational feature of the lower anchor so as to reduce play in theconnection between the upper anchor and the lower anchor.

The portion of the internal passage 39 of the upper anchor taken up bythe anti-rotational feature may vary depending upon the embodiment. Inthe embodiment of the upper anchor of the present invention illustratedin FIGS. 10 and 11, the hexagonal shaped anti-rotational feature takesup less than half of the entire length of the internal passage 39.However, the length of such an anti-rotational feature may depend uponthe length of the anti-rotational feature on the lower anchor and theamount of translational movement of the upper anchor with respect to thelower anchor that is desired.

The internal passage 39 of the upper anchor may also include a surfacefor engaging the translational screw. In the embodiment of thetranslational screw of the present invention illustrated in FIG. 11, theinner passage 39 of upper anchor 37 includes translationalscrew-engaging surface 43. The embodiment of the upper anchor 37illustrated in FIG. 11 is configured such that region of reduceddiameter 23 of the translational screw illustrated in FIGS. 6 and 7 maybe accommodated in the narrower opening 45 of internal passage 39.

According to the present invention, region 47 of the internal passage 39of the upper anchor 37 may have a wider diameter to accommodate region25 of wider diameter of the translational screw 17. The step 27 betweenthe regions 25 and 23 of the translational screw may abut surface 43 inthe internal passage 39 of the upper anchor 37 upon arranging the upperanchor over the lower anchor and the translational screw. Contactbetween these two surfaces facilitates translational movement of theupper anchor relative to the lower anchor as described below in greaterdetail.

At least a portion of the outer surface of the upper anchor may bethreaded. The threaded portion of the exterior surface of the upperanchor may engage bone forming the sidewalls of a hole made in a bone.Typically, the external threads on the upper anchor are right handed.Typically, the exterior threads on the upper anchor have the samehandedness as the exterior threads on the lower anchor.

The upper anchor may also include an indicator for indicating theposition of the upper anchor relative to the lower anchor, particularlywhen the lower anchor is fully inserted into the upper anchor. In theembodiment illustrated in FIGS. 10 and 11, the indicator includes aregion 51 having a reduced diameter as compared to the externallythreaded portion 49. The region of reduced diameter may be arranged inthe vicinity of the end 53 of the upper anchor 37 for receiving thelower anchor 1. As illustrated in FIG. 31, when a distractionosteogenesis fixture according to the present invention is assembled, ifthe upper anchor includes such a region of reduced diameter, it forms aband where the end 53 of the upper anchor abuts against the surface 11of the lower anchor 1. This reduced diameter or other indicator may helpto determine the location of the end 53 of the upper anchor of thefixture during the distraction osteogenesis process as well.

The end 55 of the upper anchor opposite the end 53 for receiving thelower anchor may include an external anti-rotational feature. Theembodiment of the upper anchor illustrated in FIGS. 10 and 11 includes aregion 57 having a hexagonal cross-sectional shape. This anti-rotationalfeature may function to engage, among other things, a fixture mount.This external anti-rotational feature of the upper anchor may be usefulwhen the distraction osteogenesis according to the present invention isto remain in place and be utilized in tooth implant applications. Ofcourse the anti-rotational feature may have configurations other than ahexagonal shape.

The upper anchor 37 may also include a flange 59. Flange 59 may be aregion having a diameter greater than the diameter of theanti-rotational feature. The flange may abut against a fixture mount orother element applied over the external anti-rotational feature of theupper anchor. The upper anchor according to the present invention mayalso include a reduced diameter collar region 61 between the flange 59and the externally threaded portion 49.

As illustrated in the close up cross-sectional view shown in FIG. 12,according to the present invention, opening of internal passage 39 atthe end 55 of the upper fixture 37 may be beveled. Additionally, theexterior surface of the upper anchor where the anti-rotational feature57 intersects with flange 59 may be stepped. Surface 63 of flange 59 maybe angled about 1° away from end 55 with increasing distance toward thecenter axis of upper anchor 37. According to the present invention,opening of internal passage 39 at end 55 of upper anchor 37 may also bebeveled.

The present invention may also include a depth gauge. The depth gaugemay be utilized to indicate the region where the bone should be cutduring the distraction osteogenesis process as described below ingreater detail. Accordingly, the depth gauge may be used to indicate thelocation where the end 53 of upper anchor 37 abuts against surface 11 oflower anchor 1. It is important to know the location of this surfacesince after securing the distraction osteogenesis fixture of the presentinvention in the bone of a patient, prior to beginning the bonestretching process, the bone stretching process will begin at the pointwhere the upper anchor becomes separated from the lower anchor. In theembodiment of the present invention illustrated in the drawings, thiswill begin to occur in the vicinity of the end of the externallythreaded portion of the upper anchor, which is indicated by theindicator as described above.

FIGS. 16 and 17 illustrate an embodiment 65 of a depth gauge accordingto the present invention. Depth gauge 65 may include slot 67 forreceiving the anti-rotational feature 57 of the upper anchor 37 therein.Slot 67 may be elongated as illustrated in FIG. 17 to permit the depthgauge to slide along the anti-rotational feature of the upper anchor,thereby accommodating various thicknesses of bone where the fixtureaccording to the present invention is installed. The short arm 73 of thedepth gauge 65 may have a position such that when depth gauge isarranged on the upper anchor 37, it will indicate the position the base53 of the upper anchor 37. The short arm 73 indicates theapical-occlusal position of the base 53 of the upper anchor 37.

The present invention may also include a retaining screw. The retainingscrew may be inserted in the inner passage of translational screw 17 forhelping to immobilize the upper anchor relative to the translationalscrew. The retaining screw may also help to provide means for rotatingthe translational screw to cause translational movement of the upperanchor relative to the lower anchor.

FIGS. 18 and 19 illustrate an embodiment of a retaining screw accordingto the present invention. The embodiment of the retaining screw 73illustrated in FIGS. 18 and 19 includes a screw head 75. The screw head75 includes slot 77 for engaging in mechanical or motor driven screwdriver for rotating the retaining screw.

The retaining screw according to the present invention may also includean externally threaded shaft 79. The handedness of the threads on theexternally threaded shaft 79 of retaining screw 73 match the handednessof the threads on the internally threaded passage 31 of retaining screw17. According to one embodiment of the present invention, the threads onthe externally threaded portion of the retaining screw and the threadson the internal passage of the translational screw 17 are right handed.According to such an embodiment, the external threads on thetranslational screw are left handed. Also according to this embodiment,when retaining screw is fully inserted in the translational screw andretaining screw is further rotated in a direction that would tighten theretaining screw in the translational screw internal passage, due to theopposite handedness of the external threads on the translational screw,translational screw will unscrew from the lower anchor thereby resultingin the translational movement of the upper anchor with respect to thelower anchor.

Typically, the head 75 of retaining screw 73 has a larger diameter thanthe diameter of the opening of the upper anchor that the section 23 ofreduced diameter of the translational screw extends through. In thismanner, the surface 81 of retaining screw cap 75 that contacts the uppersurface of the upper anchor and the step 27 of translational screwcontacting the surface 43 of the upper anchor may serve to immobilizethe upper anchor translational screw and retaining screw with respect toeach other when the retaining screw is fully inserted into the innerpassage in the translational screw and tightened therein.

The present invention may also include a healing cap for helping to sealthe opening of the distraction osteogenesis fixture of the presentinvention after implantation into a bone. A healing cap according to thepresent invention may include one or two pieces. Regardless of whetherthe healing cap includes one or two pieces, the healing cap typicallyincludes a threaded shaft for insertion into the threaded internalpassage of the translational screw as well as a portion that engages anupper surface of the upper anchor.

FIGS. 20-24 illustrate an embodiment of a two piece healing capaccording to the present invention. This embodiment includes a cap screwportion and a cap portion. The cap screw portion engages the internallythreaded passage of the translational screw.

FIG. 20 illustrates a side plan view of the cap screw 83 of the twopiece healing cap according to the present invention. Cap screw 83includes cap portion 85 and threaded shaft portion 87. As stated above,threaded shaft portion is receivable by threaded internal passage 31 oftranslational screw 17. Accordingly, the handedness of the threads ofhealing cap screw 87 preferably are complementary to the handedness ofthe threads of internal passage 31 of translational screw 17.

Typically, cap portion 85 has a width larger than the width of a passagein a healing cap portion illustrated in FIGS. 22-24. Engagement ofsurface 89 of cap portion 85 with surface 95 of cylindrical portion 93,described below in greater detail, of the two piece healing cap helps toseal the opening of the cylinder portion, in turn, the upper anchor. Capscrew portion 83 may also include a slot 91 for engaging a manual ormotor operated screw driver.

The two piece healing cap illustrated in FIGS. 20-24 also includescylinder portion 93 illustrated in FIGS. 22-24. Cylinder portion 93 mayinclude cap screw engaging surface 95. The cap screw engaging surfacemay be recessed in the top surface 97 of cylinder portion 93 as in theembodiment illustrated in FIG. 22. This may help to ensure that thehealing cap seals the distraction osteogenesis fixture according to thepresent invention.

The embodiment of the healing cap cylinder portion 93 illustrated inFIGS. 20-24 may also include a recess 99 for receiving top portion 57 ofthe upper anchor 37. Surface 101 of two piece healing cylinder portion93 may engage the surface of the flange 59 of the upper anchor to sealthe upper anchor. Cap screw portion 83 may be received by passage 103 inthe cylinder portion 93.

The present invention may also include a fixture mount for inserting thedistraction osteogenesis fixture into the bone. FIGS. 28 and 29illustrate an example of an embodiment of a fixture mount according tothe present invention. A fixture mount according to the presentinvention may include two elements. The two elements include a fixturemount screw cap 105 and a fixture mount 111. The screw cap has athreaded end 107 and a head 109. One element of the fixture mount may becylindrically shaped. The cylinder may include an internal passage.

One end 113 of the internal passage of the cylinder portion of theembodiment of the fixture mount illustrated in FIGS. 28 and 29 mayinclude a hexagonally-shaped opening to engage the hexagonal shapedexternal anti-rotational feature on the upper anchor. The opening of thefixture mount may include a structure to engage the anti-rotationalfeature on the upper anchor. The end of the cylinder opposite the end115 that engages the upper anchor may include structure for engaging amanual or motorized torque transfer device for driving the distractionosteogenesis fixture into the bone by rotation.

A distraction osteogenesis fixture according to the present inventionmay also include a manual fixture counter torque element. An embodimentof a manual fixture counter torque element according to the presentinvention is illustrated in FIGS. 25-27. The manual fixture countertorque element 117 includes an anti-rotational feature 119 for mating tothe anti-rotational feature of the upper anchor.

The manual fixture counter torque element may also include features forapplying torque to the element and as a result, the upper anchor of thedistraction osteogenesis fixture. For example, as illustrated in theembodiment shown in FIG. 26, the manual fixture counter torque mayinclude a textured handle region 121.

The manual fixture counter torque may also include a ligature hole 123.The ligature hole engages a suture, preventing the fixture countertorque element from accidental loss in the patient's throat.

FIGS. 30-34 illustrate assembly of a distraction osteogenesis fixtureaccording to the present invention. Along these lines, FIG. 30illustrates an embodiment of a distraction osteogenesis fixtureaccording to the present invention showing assembly of the lower anchorand the translational screw. On the other hand, FIG. 31 illustrates afully assembled distraction osteogenesis fixture including the upperanchor and lower anchor and translational screw. Additionally, FIG. 32illustrates an embodiment of the distraction osteogenesis fixtureaccording to the present invention wherein the retaining screw has beeninserted into the translational screw and the upper anchor partiallytranslated from the lower anchor. Furthermore, FIG. 33 illustrates anembodiment of the present invention including a healing cap connected tothe upper anchor and translational screw wherein the upper anchor hasbeen translated a distance on the lower anchor. Still further, FIG. 34illustrates an example of a distraction osteogenesis fixture with afixture mount attached to the upper anchor and translational screw.

Unlike distraction osteogenesis devices that are applied to the outersurface of the bone, the present invention is inserted inside the bone.A fixture according to the present invention may be made of abiocompatible material such as titanium. The fixture can be made forpermanent installation. Along these lines, it is common after stretchingfor the fixture to be used as a normal dental implant screw with anabutment and prosthetic device attached, such as a tooth. On the otherhand, the present invention may be made of a resorbable material so thatafter distraction csteogenesis, the distraction osteogenesis fixture isresorbed into the bone tissue.

The present invention also includes a distraction osteogenesis method.According to the method of the present invention, a hole may be formedin a bone of a patient. Typically, the present invention is utilized indental applications. Therefore, the hole is formed in the jawbone in apatient.

Next, a distraction osteogenesis fixture, including a lower anchor,translational screw, an upper anchor may be inserted into the hole byscrewing it into the hole. To facilitate the insertion of thedistraction osteogenesis fixture into the hole formed in the bone, afixture mount may be attached to the distraction osteogenesis fixture.The pre-assembled lower anchor, upper anchor and translational screw arescrewed into the hole in the bone to the desired level. Next, the bonemay be cut.

To facilitate cutting of the bone, a depth gauge as described above maybe arranged on the upper anchor. Typically, the cortical bone only isthen cut at the level where the end of the upper anchor abuts againstthe lower anchor. The depth gauge may help to determine the level atwhich the bone should be cut. In addition to horizontal cuts, verticalcuts may be made in the bone. In cutting bone, typically, only thecortical or hard portion of the bone is cut, leaving the softer,vascularized underlying bone portion, including nerves, intact.

After cutting the bone, the translational screw may be rotated to causethe upper anchor to move relative to the lower anchor. A retaining screwmay be utilized as described above to assist in this process. The ratethat the upper anchor may be moved relative to the lower anchor may varydepending upon the characteristics of the patient's bone. According toone embodiment of a method according to the present invention, the upperanchor is moved relative to the lower anchor about 1 mm per day.However, any desired rate may be employed. Along these lines, the ratethat the upper anchor is moved relative to the lower anchor may be fromabout 0.5 mm to about 1 mm per day.

The fixtures may be moved more than once each day. Alternatively, morethan one day may elapse between relative movements of the fixtures. Thetime period between relative movements of the fixtures may vary.

After the upper anchor is moved to the desired amount relative to thelower anchor, the distraction osteogenesis fixture according to thepresent invention may be permitted to sit stationary so that the spacescreated by movement of the upper anchor relative to the lower anchor maybe filled in with new bone. Typically this is accomplished in a periodof about 90 to about 180 days. After sitting for sufficient time topermit bone to fill in the spaces created by the present invention, anabutment and prosthetic tooth or bridge may be affixed to the fixture ofthe present invention. Alternatively, the fixture according to thepresent invention will be resorbed into the bone.

As stated above, the cortical bone may be cut, leaving bone marrowintact. FIGS. 35 and 36 provide x-ray images illustrating a fixtureaccording to the present invention implanted in the jawbone of apatient. According to FIG. 35, the upper anchor has been moved about 0.5mm with respect to the lower anchor. FIG. 36 provides an x-ray imageillustrating the patient shown in FIG. 35 wherein the upper anchor hasbeen moved a total of about 4.5 mm.

The foregoing description of the invention illustrates and describes thepresent invention. Additionally, the disclosure shows and describes onlythe preferred embodiments of the invention, but as aforementioned, it isto be understood that the invention is capable of use in various othercombinations, modifications, and environments and is capable of changesor modifications within the scope of the inventive concept as expressedherein, commensurate with the above teachings, and/or the skill orknowledge of the relevant art. The embodiments described hereinabove arefurther intended to explain best modes known of practicing the inventionand to enable others skilled in the art to utilize the invention insuch, or other, embodiments and with the various modifications requiredby the particular applications or uses of the invention. Accordingly,the description is not intended to limit the invention to the formdisclosed herein. Also, it is intended that the appended claims beconstrued to include alternative embodiments.

We claim:
 1. A distraction osteogenesis fixture, comprising: a loweranchor to be anchored in a bone, at least a portion of the lower anchorincluding external bone-engaging threads, at least a portion of thelower anchor also including an anti-rotational feature, the lower anchorincluding an internal passage, at least a portion of the internalpassage being threaded; a translational screw, at least a portion of thetranslational screw being externally threaded such that thetranslational screw is receivable by the threaded internal passage ofthe lower anchor; an upper anchor to be anchored in bone and includingan internal passage for receiving a portion of the lower anchor andhaving an anti-rotational feature for engaging the anti-rotationalfeature of the lower anchor, the internal passage of the upper anchorincluding a surface for engaging the translational screw, at least aportion of the upper anchor including external bone-engaging threads;and wherein the translational screw further includes a threaded internalpassage in the vicinity of a first end and wherein the externallythreaded portion of the translational screw extends from in the vicinityof a second end.
 2. The fixture according to claim 1, wherein thethreads of the threaded internal passage are right-handed.
 3. Adistraction osteogenesis fixture, comprising: a lower anchor to beanchored in a bone, at least a portion of the lower anchor includingexternal bone-engaging threads, at least a portion of the lower anchoralso including an anti-rotational feature, the lower anchor including aninternal passage, at least a portion of the internal passage beingthreaded; a translational screw, at least a portion of the translationalscrew being externally threaded such that the translational screw isreceivable by the threaded internal passage of the lower anchor; anupper anchor to be anchored in bone and including an internal passagefor receiving a portion of the lower anchor and having ananti-rotational feature for engaging the anti-rotational feature of thelower anchor, the internal passage of the upper anchor including asurface for engaging the translational screw, at least a portion of theupper anchor including external bone-engaging threads; wherein thetranslational screw further includes an external cylindrical surface inthe vicinity of a first end, the external cylindrical surface includingtwo regions having different diameters such that a step between the tworegions engages the translational screw engaging surface of the upperanchor; and wherein the translational screw further includes afrustoconical region arranged between the two different diameterregions.
 4. A distraction osteogenesis fixture, comprising: a loweranchor to be anchored in a bone, at least a portion of the lower anchorincluding external bone-engaging threads, at least a portion of thelower anchor also including an anti-rotational feature, the lower anchorincluding an internal passage, at least a portion of the internalpassage being threaded; a translational screw, at least a portion of thetranslational screw being externally threaded such that thetranslational screw is receivable by the threaded internal passage ofthe lower anchor; an upper anchor to be anchored in bone and includingan internal passage for receiving a portion of the lower anchor andhaving an anti-rotational feature for engaging the anti-rotationalfeature of the lower anchor, the internal passage of the upper anchorincluding a surface for engaging the translational screw, at least aportion of the upper anchor including external bone-engaging threads;and further comprising: a retaining screw for retaining the upper anchoron the translational screw, wherein the translational screw includes anthreaded internal passage for receiving the retaining screw, wherein theretaining screw fixes the upper anchor with respect to the translationalscrew.
 5. The fixture according to claim 4, wherein the retaining screwand the translational screw threaded internal passage both haveright-handed threads, such that after fixing of the upper anchor and thetranslational screw rotation of the retaining screw rotates thetranslational screw thereby causing displacement of the translationalscrew and the upper anchor relative to the lower anchor.
 6. The fixtureaccording to claim 4, wherein the retaining screw head has a diametergreater than a diameter of an opening of the internal passage of theupper anchor.
 7. A distraction osteogenesis fixture, comprising: a loweranchor to be anchored in a bone, at least a portion of the lower anchorincluding external bone-engaging threads, at least a portion of thelower anchor also including an anti-rotational feature, the lower anchorincluding an internal passage, at least a portion of the internalpassage being threaded; a translational screw, at least a portion of thetranslational screw being externally threaded such that thetranslational screw is receivable by the threaded internal passage ofthe lower anchor; an upper anchor to be anchored in bone and includingan internal passage for receiving a portion of the lower anchor andhaving an anti-rotational feature for engaging the anti-rotationalfeature of the lower anchor, the internal passage of the upper anchorincluding a surface for engaging the translational screw, at least aportion of the upper anchor including external bone-engaging threads;and further comprising: a depth gauge attached to a first end of theupper end of the upper anchor for indicating a location of a second endof the upper anchor.
 8. A distraction osteogenesis fixture, comprising:a lower anchor to be anchored in a bone, at least a portion of the loweranchor including external bone-engaging threads, at least a portion ofthe lower anchor also including an anti-rotational feature, the loweranchor including an internal passage, at least a portion of the internalpassage being threaded; a translational screw, at least a portion of thetranslational screw being externally threaded such that thetranslational screw is receivable by the threaded internal passage ofthe lower anchor; an upper anchor to be anchored in bone and includingan internal passage for receiving a portion of the lower anchor andhaving an anti-rotational feature for engaging the anti-rotationalfeature of the lower anchor, the internal passage of the upper anchorincluding a surface for engaging the translational screw, at least aportion of the upper anchor including external bone-engaging threads;and further comprising: a healing cap including an externally threadedshaft and a cap, wherein the translational screw includes a threadedinternal passage for receiving the shaft of the healing cap.
 9. Thefixture according to claim 8, wherein the shaft of the healing cap andthe threaded internal passage of the translational screw includingright-handed threads.
 10. The fixture according to claim 8, wherein thehealing cap includes screw portion that includes the threaded shaft anda separate cylindrical portion including a passage for receiving thethreaded shaft of the screw portion.
 11. A distraction osteogenesisfixture, comprising: a lower anchor to be anchored in a bone, at least aportion of the lower anchor including external bone-engaging threads, atleast a portion of the lower anchor also including an anti-rotationalfeature, the lower anchor including an internal passage, at least aportion of the internal passage being threaded; a translational screw,at least a portion of the translational screw being externally threadedsuch that the translational screw is receivable by the threaded internalpassage of the lower anchor; an upper anchor to be anchored in bone andincluding an internal passage for receiving a portion of the loweranchor and having an anti-rotational feature for engaging theanti-rotational feature of the lower anchor, the internal passage of theupper anchor including a surface for engaging the translational screw,at least a portion of the upper anchor including external bone-engagingthreads; and further comprising: a fixture mount including a threadedshaft, wherein the translational screw includes a threaded internalpassage for receiving the shaft of the fixture mount, the fixture mountfurther including a fixture receiving member.
 12. The fixture accordingto claim 11, wherein the threaded internal passage of the translationalscrew and the threaded shaft of the fixture mount include right-handedthreads.
 13. The fixture according to claim 11, wherein the upper anchorfurther includes an external anti-rotational feature, and the fixturemount further includes an internal anti-rotational feature for engagingthe external anti-rotational feature of the upper anchor.
 14. Adistraction osteogenesis fixture, comprising: a lower anchor to beanchored in a bone, at least a portion of the lower anchor includingexternal bone-engaging threads, at least a portion of the lower anchoralso including an anti-rotational feature, the lower anchor including aninternal passage, at least a portion of the internal passage beingthreaded; a translational screw, at least a portion of the translationalscrew being externally threaded such that the translational screw isreceivable by the threaded internal passage of the lower anchor; anupper anchor to be anchored in bone and including an internal passagefor receiving a portion of the lower anchor and having ananti-rotational feature for engaging the anti-rotational feature of thelower anchor, the internal passage of the upper anchor including asurface for engaging the translational screw, at least a portion of theupper anchor including external bone-engaging threads; and furthercomprising: a manual fixture counter torque member attached to the upperanchor and including at least one element for engaging an apparatus forapplying torque to the fixture, wherein the upper anchor furtherincludes an external anti-rotational feature, and the manual fixturecounter torque member further includes an internal anti-rotationalfeature for engaging the external anti-rotational feature of the upperanchor.
 15. A distraction osteogenesis method, comprising the steps of:forming a hole in a bone of a patient; inserting a pre-assembleddistraction osteogenesis fixture into the hole, the osteogenesis fixturecomprising a lower anchor, a translation screw and an upper anchor,wherein the lower anchor includes an externally threaded portion, ananti-rotational feature, and a threaded internal passage, wherein thetranslational screw includes an externally threaded portion receivableby the threaded internal passage of the lower anchor, and wherein theupper anchor includes an internal passage for receiving a portion of thelower anchor and having an anti-rotational feature for engaging theanti-rotational feature of the lower anchor, the internal passage of theupper anchor including a surface for engaging the translational screw,at least a portion of the upper anchor being externally threaded;cutting at least the cortical portion of the bone; and rotating thetranslational screw so as to cause linear translational movement of theupper anchor relative to the lower anchor, thereby distancing the bonesurrounding the upper anchor from the bone surrounding the lower anchor.16. The method according to claim 15, wherein the bone is a jawbone.